Geothermal

Martin Saar and his research at the University of Minnesota is in the news! Saar’s research has led to new technology and a start-up. He was originally funded by the Initiative for Renewable Energy and the Environment (IREE) in 2009. The initial research resulted in a major federal grant from the U.S. Department of Energy as part of the American Recovery and Reinvestment Act (ARRA).

CO2-based geothermal energy has only recently entered renewable energy discussions. Research by Martin Saar and his team is attempting to establish Minnesota as a center for interdisciplinary and comprehensive research on the topic which position Minnesota as a world leader. Minnesota exemplifies many regions worldwide (e.g., north-central and north-eastern America, parts of central and northern Europe) where geothermal energy use is currently restricted to space/water heating via heat pumps because of low geothermal heat flow. However, the approach used in Saar’s research is expected to enable substantial subsurface heat extraction even from regions such as Minnesota and is particularly efficient during cold atmospheric temperatures (e.g., Minnesota winters). This project will:

Take advantage of the geology, heat-flow characteristics and climate patterns that are typical of Minnesota and beneficial to the proposed study.

Incorporate external collaborators who are recognized as experts in their fields and have ties to the University of Minnesota.

Recognize the opportunities presented by the substantial size of the University of Minnesota with its many departments that are relevant to this interdisciplinary study.

Drs. Martin Saar and Jimmy Randolph have had a paper accepted to Geophysical Research Letters on the feasibility of developing an enhanced geothermal power plant system that generates electricity in low to intermediate heat flow regions like Minnesota while simultaneously sequestering carbon dioxide in the ground.

IREE supported this research via a $600,000 Large Grant, and the project has leveraged just over $1.7M.

Abstract
Geothermal energy offers clean, renewable, reliable electric power with no need for grid‐scale energy storage, yet its use has been constrained to the few locations worldwide with naturally high geothermal heat resources and groundwater availability. We present a novel approach with the potential to permit expansion of geothermal energy utilization: heat extraction from naturally porous, permeable formations with CO2 as the injected subsurface working fluid.

Fluid‐mechanical simulations reveal that the significantly higher mobility of CO2, compared to water, at the temperature/pressure conditions of interest makes CO2 an attractive heat exchange fluid. We show numerically that, compared to conventional water‐based and engineered geothermal systems, the proposed approach provides up to factors of 2.9 and 5.0, respectively, higher geothermal heat energy extraction rates. Consequently, more regions worldwide could be economically used for geothermal electricity production. Furthermore, as the injected CO2 is eventually geologically sequestered, such power plants would have negative carbon footprints.

IREE recently funded a project, led by UMN Geology & Geophysics professor Martin Saar, which leveraged $1.5M from the Department of Energy. IREE’s initial investment was $150,000. The project focuses on advancing the concept of a carbon dioxide-sequestering geothermal power plant. This type of plant would be carbon negative. That is, it would actually remove carbon dioxide from the atmosphere that is emitted from carbon-burning power plants and other plants that emit carbon dioxide while providing an efficient, environmentally friendly source of electricity.

In addition to aiding in carbon dioxide removal and “clean” electricity, this technology would also improve the efficiency of geothermal systems, thus extending the potential use to areas currently considered unsuitable for geothermal energy extraction.